我正在制作一个搜索SQLite数据库中的餐馆的Android应用程序。我目前使用自定义加载器（我在网上找到）从数据库加载游标，然后使用该游标并使用SimpleCursorAdapter填充列表视图。我希望绑定所有数据，但只显示要显示的餐馆名称（因为当我点击列表项时，我想获取所有数据并将其发送到显示数据的新活动）。如果我指定餐馆名称和餐馆类型作为搜索参数，我运行原始查询：
"SELECT * FROM Restaurant WHERE name = " + name + " AND rType = " + restaurantType;
在我的SQLiteCursorLoader类中，我收到一条错误，指出列rType不存在，即使我知道该列存在于Restuarant表中。当我在查询中有两个WHERE子句时，我似乎得到了这个错误，但是当我有一个WHERE子句时，这不会发生。任何帮助将不胜感激！这是我的代码：
RestuarantSearchResultsActivity：
package com.studentapplication;
import android.app.Activity;
import android.app.ListActivity;
import android.app.LoaderManager;
import android.content.Loader;
import android.database.Cursor;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
public class RestaurantSearchResultsActivity extends ListActivity implements
LoaderManager.LoaderCallbacks<Cursor>{
DatabaseHelper databaseHelper;
SimpleCursorAdapter mAdapter;
Bundle searchParameters;
@Override
public void onCreate(Bundle savedInstanceState)
{
Log.w("CoolBeans", "Results Activity Created");
super.onCreate(savedInstanceState);
databaseHelper = new DatabaseHelper(getApplicationContext());
//setContentView(R.layout.restaurant_search_results);
Bundle searchParameters = getIntent().getExtras();
String n = searchParameters.getString("name");
Log.i("0)", n);
//first N columns should match toViews first N views
String[] fromColumns = {getString(R.string.database_column_name),
getString(R.string.database_column_restaurant_type),
getString(R.string.database_column_phone_number),
getString(R.string.database_column_address),
getString(R.string.database_column_csz),
getString(R.string.database_column_brief_description),
getString(R.string.database_column_url),
getString(R.string.database_column_price)};
int[] toViews = {android.R.id.text1};
mAdapter = new SimpleCursorAdapter( getApplicationContext(),
this.getListView().getId(),
null,
fromColumns,
toViews,
0);
setListAdapter(mAdapter);
getLoaderManager().initLoader(0, searchParameters, this);
}
@Override
public Loader<Cursor> onCreateLoader(int id, Bundle searchParameters) {
Log.i("3)", "Correct Loader Being Built");
return new SQLiteCursorLoader(getApplicationContext(),
databaseHelper,
searchParameters,
null);
}
@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
mAdapter.swapCursor(data);
}
@Override
public void onLoaderReset(Loader<Cursor> loader) {
mAdapter.swapCursor(null);
}
@Override
public void onListItemClick(ListView l, View v, int position, long id)
{
Cursor myCursor = (Cursor)l.getItemAtPosition(position);
if(l.isItemChecked(position) == true)
{
l.setItemChecked(position, false);
//shut down previously selected item details
}
else
{
l.setItemChecked(position, true);
//start previously selected item details
}
}
}
SQLiteCursorLoader：
package com.studentapplication;
import java.io.FileDescriptor;
import java.io.PrintWriter;
import java.util.Arrays;
import android.content.ContentValues;
import android.content.Context;
import android.content.res.Resources;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteQueryBuilder;
import android.os.Bundle;
import android.util.Log;
public class SQLiteCursorLoader extends AbstractCursorLoader
{
SQLiteOpenHelper db=null;
String rawQuery=null;
String[] args=null;
/**
* Creates a fully-specified SQLiteCursorLoader. See
* {@link SQLiteDatabase#rawQuery(SQLiteDatabase, String, String[])
* SQLiteDatabase.rawQuery()} for documentation on the
* meaning of the parameters. These will be passed as-is
* to that call.
*/
public SQLiteCursorLoader(Context context, SQLiteOpenHelper db, Bundle
searchParameters, String[] args)
{
super(context);
this.db=db;
this.rawQuery=createQuery(searchParameters);
this.args=args;
}
private String createQuery(Bundle searchParameters) {
String name = "\'";
name = name + searchParameters.getString("name");
name = name + "\'";
int price = searchParameters.getInt("price");
String restaurantType = "\'";
restaurantType = restaurantType +
searchParameters.getString("restaurant_type");
restaurantType = restaurantType + "\'";
//String dist = searchParameters.getString("dist");
String theQuery = "";
if(!name.equals("\'\'"))
{
if(!restaurantType.equals("\'_\'"))
{
theQuery = "SELECT * FROM Restaurant WHERE name
= "+ name + " AND rType = " + restaurantType;
}
else if(price != 0)
{
theQuery = "SELECT * FROM Restaurant WHERE name = " + name
+ " AND price = " + ((Integer)price).toString();
}
else
{
theQuery="SELECT * FROM Restaurant WHERE name = " + name;
}
}
else if(!restaurantType.equals("\'\'"))
{
theQuery = "SELECT * FROM Restaurant WHERE type = " +
restaurantType + " SORT BY name";
}
else if(price != 0)
{
theQuery="SELECT * FROM Restaurant WHERE price=" + price + " SORT
BY name";
}
return theQuery;
}
/**
* Runs on a worker thread and performs the actual
* database query to retrieve the Cursor.
*/
@Override
protected Cursor buildCursor()
{
return(db.getReadableDatabase().rawQuery(rawQuery, args));
}
/**
* Writes a semi-user-readable roster of contents to
* supplied output.
*/
@Override
public void dump(String prefix, FileDescriptor fd, PrintWriter writer, String[]
args)
{
super.dump(prefix, fd, writer, args);
writer.print(prefix);
writer.print("rawQuery=");
writer.println(rawQuery);
writer.print(prefix);
writer.print("args=");
writer.println(Arrays.toString(args));
}
public void insert(String table, String nullColumnHack, ContentValues values)
{
new InsertTask(this).execute(db, table, nullColumnHack, values);
}
public void update(String table, ContentValues values, String whereClause, String[]
whereArgs)
{
new UpdateTask(this).execute(db, table, values, whereClause, whereArgs);
}
public void replace(String table, String nullColumnHack, ContentValues values)
{
new ReplaceTask(this).execute(db, table, nullColumnHack, values);
}
public void delete(String table, String whereClause, String[] whereArgs)
{
new DeleteTask(this).execute(db, table, whereClause, whereArgs);
}
public void execSQL(String sql, Object[] bindArgs)
{
new ExecSQLTask(this).execute(db, sql, bindArgs);
}
//Private Classes
private class InsertTask extends ContentChangingTask<Object, Void, Void>
{
InsertTask(SQLiteCursorLoader loader)
{
super(loader);
}
@Override
protected Void doInBackground(Object... params)
{
SQLiteOpenHelper db=(SQLiteOpenHelper)params[0];
String table=(String)params[1];
String nullColumnHack=(String)params[2];
ContentValues values=(ContentValues)params[3];
db.getWritableDatabase().insert(table, nullColumnHack, values);
return(null);
}
}
private class UpdateTask extends ContentChangingTask<Object, Void, Void>
{
UpdateTask(SQLiteCursorLoader loader)
{
super(loader);
}
@Override
protected Void doInBackground(Object... params)
{
SQLiteOpenHelper db=(SQLiteOpenHelper)params[0];
String table=(String)params[1];
ContentValues values=(ContentValues)params[2];
String where=(String)params[3];
String[] whereParams=(String[])params[4];
db.getWritableDatabase().update(table, values, where, whereParams);
return(null);
}
}
private class ReplaceTask extends ContentChangingTask<Object, Void, Void>
{
ReplaceTask(SQLiteCursorLoader loader)
{
super(loader);
}
@Override
protected Void doInBackground(Object... params)
{
SQLiteOpenHelper db=(SQLiteOpenHelper)params[0];
String table=(String)params[1];
String nullColumnHack=(String)params[2];
ContentValues values=(ContentValues)params[3];
db.getWritableDatabase().replace(table, nullColumnHack, values);
return(null);
}
}
private class DeleteTask extends ContentChangingTask<Object, Void, Void>
{
DeleteTask(SQLiteCursorLoader loader)
{
super(loader);
}
@Override
protected Void doInBackground(Object... params)
{
SQLiteOpenHelper db=(SQLiteOpenHelper)params[0];
String table=(String)params[1];
String where=(String)params[2];
String[] whereParams=(String[])params[3];
db.getWritableDatabase().delete(table, where, whereParams);
return(null);
}
}
private class ExecSQLTask extends ContentChangingTask<Object, Void, Void>
{
ExecSQLTask(SQLiteCursorLoader loader)
{
super(loader);
}
@Override
protected Void doInBackground(Object... params)
{
SQLiteOpenHelper db=(SQLiteOpenHelper)params[0];
String sql=(String)params[1];
Object[] bindParams=(Object[])params[2];
db.getWritableDatabase().execSQL(sql, bindParams);
return(null);
}
}
}
AbstractCursorLoader：
package com.studentapplication;
import android.annotation.TargetApi;
import android.content.AsyncTaskLoader;
import android.content.Context;
import android.database.Cursor;
import android.os.Build;
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
abstract public class AbstractCursorLoader extends AsyncTaskLoader<Cursor> {
abstract protected Cursor buildCursor();
Cursor lastCursor=null;
public AbstractCursorLoader(Context context) {
super(context);
}
/**
* Runs on a worker thread, loading in our data. Delegates
* the real work to concrete subclass' buildCursor() method.
*/
@Override
public Cursor loadInBackground() {
Cursor cursor=buildCursor();
if (cursor!=null) {
// Ensure the cursor window is filled
cursor.getCount();
}
return(cursor);
}
/**
* Runs on the UI thread, routing the results from the
* background thread to whatever is using the Cursor
* (e.g., a CursorAdapter).
*/
@Override
public void deliverResult(Cursor cursor) {
if (isReset()) {
// An async query came in while the loader is stopped
if (cursor!=null) {
cursor.close();
}
return;
}
Cursor oldCursor=lastCursor;
lastCursor=cursor;
if (isStarted()) {
super.deliverResult(cursor);
}
if (oldCursor!=null && oldCursor!=cursor && !oldCursor.isClosed()) {
oldCursor.close();
}
}
/**
* Starts an asynchronous load of the list data.
* When the result is ready the callbacks will be called
* on the UI thread. If a previous load has been completed
* and is still valid the result may be passed to the
* callbacks immediately.
*
* Must be called from the UI thread.
*/
@Override
protected void onStartLoading() {
if (lastCursor!=null) {
deliverResult(lastCursor);
}
if (takeContentChanged() || lastCursor==null) {
forceLoad();
}
}
/**
* Must be called from the UI thread, triggered by a
* call to stopLoading().
*/
@Override
protected void onStopLoading() {
// Attempt to cancel the current load task if possible.
cancelLoad();
}
/**
* Must be called from the UI thread, triggered by a
* call to cancel(). Here, we make sure our Cursor
* is closed, if it still exists and is not already closed.
*/
@Override
public void onCanceled(Cursor cursor) {
if (cursor!=null && !cursor.isClosed()) {
cursor.close();
}
}
/**
* Must be called from the UI thread, triggered by a
* call to reset(). Here, we make sure our Cursor
* is closed, if it still exists and is not already closed.
*/
@Override
protected void onReset() {
super.onReset();
// Ensure the loader is stopped
onStopLoading();
if (lastCursor!=null && !lastCursor.isClosed()) {
lastCursor.close();
}
lastCursor=null;
}
}
DatabaseHelper：
package com.studentapplication;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
public class DatabaseHelper extends SQLiteOpenHelper {
// All Static variables
// Database Version
private static final int DATABASE_VERSION = 1;
// Database Name
private static final String DATABASE_NAME = "LOCAL_DATABASE";
// table Names
private static final String TABLE_Restaurant = "Restaurant";
private static final String TABLE_Coupon = "Coupon";
private static final String TABLE_Linker = "Linker";
//restaurant columns
private static final String R_Name = "name";
private static final String R_Description = "description";
private static final String R_Address = "address";
private static final String R_CSZ = "CSZ";
private static final String R_URL = "url";
private static final String R_Price = "price";
private static final String R_Type = "rType";
private static final String R_ID = "_id";
//coupon columns
private static final String C_ID = "_id";
private static final String C_NAME = "name";
private static final String C_Description = "description";
//linker table columns
private static final String r_id = "r_id";
private static final String c_id = "c_id";
private static final String date = "date";
private static final String l_id = "l_id";
public DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
public DatabaseHelper(Context context, String name, CursorFactory factory,
int version) {
super(context, name, factory, version);
}
// Creating Tables
@Override
public void onCreate(SQLiteDatabase db) {
String CREATE_Restaurant_TABLE = "CREATE TABLE " + TABLE_Restaurant + "( "
+ R_ID + " INTEGER PRIMARY KEY, "
+ R_Name + " TEXT NOT NULL, "
+ R_Type + " TEXT NOT NULL, "
+ R_Address + " TEXT NOT NULL, "
+ R_CSZ + " TEXT NOT NULL, "
+ R_Description + " TEXT NOT NULL, "
+ R_URL + " TEXT NOT NULL, "
+ R_Price +" INTEGER NOT NULL"
+ " )";
String CREATE_Coupon_TABLE = "CREATE TABLE " + TABLE_Coupon + "("
+ C_ID + " INTEGER PRIMARY KEY, "
+ C_NAME + " TEXT, "
+ C_Description + " TEXT"
+ ")";
String CREATE_Linker_TABLE = "CREATE TABLE " + TABLE_Linker + "("
+ r_id + " INTEGER, "
+ c_id + " INTEGER, "
+ date + " DATE, "
+ l_id + "INTEGER PRIMARY KEY, "
+ "FOREIGN KEY(r_id) REFERENCES Restaurant(_id), "
+ "FOREIGN KEY(c_id) REFERENCES Coupon(_id) )";
db.execSQL(CREATE_Restaurant_TABLE);
db.execSQL(CREATE_Coupon_TABLE);
db.execSQL(CREATE_Linker_TABLE);
}
// Upgrading database
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Drop older table if existed
db.execSQL("DROP TABLE IF EXISTS " + TABLE_Restaurant);
// Create tables again
onCreate(db);
}
}
堆栈追踪：
04-23 13:47:29.691: E/SQLiteLog(2600): (1) no such column: rType
04-23 13:47:29.691: W/dalvikvm(2600): threadid=11: thread exiting with uncaught
exception (group=0x40a13300)
04-23 13:47:29.852: E/AndroidRuntime(2600): FATAL EXCEPTION: AsyncTask #1
04-23 13:47:29.852: E/AndroidRuntime(2600): java.lang.RuntimeException: An error
occured while executing doInBackground()
04-23 13:47:29.852: E/AndroidRuntime(2600): at
android.os.AsyncTask$3.done(AsyncTask.java:299)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
java.util.concurrent.FutureTask.setException(FutureTask.java:124)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
java.util.concurrent.FutureTask.run(FutureTask.java:137)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
java.lang.Thread.run(Thread.java:856)
04-23 13:47:29.852: E/AndroidRuntime(2600): Caused by:
android.database.sqlite.SQLiteException: no such column: rType (code 1): , while
compiling: SELECT * FROM Restaurant WHERE name = 'RName' AND rType = 'Fancy'
04-23 13:47:29.852: E/AndroidRuntime(2600): at
android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
android.database.sqlite.SQLiteConnection.acquirePreparedStatement
(SQLiteConnection.java:882)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:493)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
android.database.sqlite.SQLiteDirectCursorDriver.query
(SQLiteDirectCursorDriver.java:44)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1314)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1253)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
com.studentapplication.SQLiteCursorLoader.buildCursor(SQLiteCursorLoader.java:88)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
com.studentapplication.AbstractCursorLoader.loadInBackground
(AbstractCursorLoader.java:24)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
com.studentapplication.AbstractCursorLoader.loadInBackground
(AbstractCursorLoader.java:1)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
android.content.AsyncTaskLoader.onLoadInBackground(AsyncTaskLoader.java:301)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
android.content.AsyncTaskLoader$LoadTask.doInBackground(AsyncTaskLoader.java:68)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
android.content.AsyncTaskLoader$LoadTask.doInBackground(AsyncTaskLoader.java:56)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
android.os.AsyncTask$2.call(AsyncTask.java:287)
04-23 13:47:29.852: E/AndroidRuntime(2600): at
java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
04-23 13:47:29.852: E/AndroidRuntime(2600): ... 4 more
04-23 13:47:29.902: W/ActivityManager(161): Force finishing activity
com.studentapplication/.RestaurantSearchResultsActivity
04-23 13:47:29.902: W/WindowManager(161): Failure taking screenshot for (266x425) to
layer 21020
答案 0 :(得分：0)
在生产环境中，当您修改数据库的架构时，会突显传递给SQLiteOpenHelper构造函数的架构版本号，因此SQLiteOpenHelper将调用onUpgrade()并影响更改。
在开发过程中，如果您愿意，也可以这样做。但是，很容易忘记这一点。因此，如果您的数据库结构似乎不符合预期，则：
将模式版本号颠覆，以强制onUpgrade()来电，或
通过卸载，“设置”等应用条目中的“清除数据”清除现有数据库，以强制拨打onCreate()的{{1}}